Saudi Cultural Missions Theses & Dissertations
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Item Restricted Microwave Assisted Synthesis of Au/TiO2 Catalyst for Photocatalysis and Oxidation Processes(Cardiff University, 2024) Alazmi, Abdullah Mubarak S; Edwards, JenniferHeterogeneous catalysis using supported metal nanoparticles has attracted tremendous interest for applications including photocatalysis and selective oxidations. This work focuses on synthesis and characterization of Au nanoparticles supported on TiO2 (Au/TiO2), which exhibits unique photocatalytic and catalytic properties arising from quantum and plasmonic effects of Au as well as strong metal-support interactions. A facile microwave-assisted polyol approach was used to prepare Au/TiO2 with 0.1-3 wt% Au loading. Structural characterization by XRD revealed anatase TiO2 support was retained after Au deposition. Au particle size increased from sub nm clusters at 0.1 wt% to 13.5 nm nanoparticles at 3 wt% loading, demonstrating tunable nanoparticle dimensions. CO oxidation testing showed highest mass activity for 0.5 wt% Au/TiO2, with declining performance at higher loadings attributed to loss of low-coordination sites through agglomeration. Photocatalytic degradation of methyl orange dye was most efficient with 0.5 wt% Au/TiO2 under simulated solar irradiation. The higher photoactivity is ascribed to improved visible light harvesting and minimized charge recombination from uniform deposition of small plasmonic Au nanoparticles. The results demonstrate optimized Au loading and dispersion governs both catalytic and photocatalytic efficiency of Au/TiO2 synthesized via microwave polyol method.11 0Item Restricted Polymers for Energy‐efficient Membrane Separations(University of Manchester, 2024) Aloraini, Sulaiman Ibrahim S; Budd, Peter MAdvanced membrane materials have come under increased scrutiny due to the growing need for environmentally friendly and economically viable gas and organic solvent separation processes. Among them, Polymers of Intrinsic Microporosity (PIMs) are particularly noteworthy because of their high free volume and remarkable permeability, which make them ideal candidates for separation processes. However, despite their outstanding permeability and selectivity, long-term stability issues, particularly under harsh conditions and physical aging, have hindered their widespread adoption. This research seeks to address these challenges by investigating innovative approaches to enhance the performance and durability of membranes based on the prototypical PIM, referred to as PIM-1. A variety of modification options are investigated in this work with the goal of improving PIM-1 membrane stability and overall separation efficiency. These tactics include crosslinking PIM-1 with palladium acetate, functionalising PIM-1 with diethanolamine (DEA), and blending with polyethyleneimine (PEI) to enhance stability in organic solvents. The crosslinking process, in particular, leads to significant improvements in mechanical properties and solvent resistance, making the membranes more suitable for applications such as pervaporation of organic-organic mixtures and phenol removal via perstraction. The use of these modified PIM-1 membranes in pervaporation is exemplified by the separation of toluene from dimethyl sulfoxide mixtures. Crosslinked PIM-1 membranes demonstrated increased flux throughout the separation process, markedly surpassing conventional membranes. Furthermore, the functionalisation of PIM-1 with DEA enhanced selectivity, especially in the separation of methanol from organic solvents. The process of perstraction demonstrates the efficacy of PIM-1 membranes in extracting phenol from aqueous solutions, underscoring the benefits of crosslinking, which result in improved selectivity and stability during prolonged operation. This research not only enhances comprehension of PIM-1-based membrane modifications but also provides practical insights into their industrial applications, thereby facilitating the development of more efficient separation technologies for challenging solvent environments.8 0Item Restricted LIQUID CRYSTALS NUCLEI COEXISTING WITH AN ISOTROPIC PHASE(Kent State University, 2022-08) Alqarni, Ali; Lavrentovich, OlegThe morphology of finite-size condensed materials is influenced by surface tension. To reduce surface area, tiny droplets of water in the air have spherical shapes, but solid crystals have facetted shapes defined by the orientation dependency of surface tension. Bulk interactions are unimportant in these two examples because they are either too weak to overcome surface tension in the first case or too powerful to enable internal curvatures in the second case. In liquid crystal droplets, the bulk and surface energies are more closely balanced, resulting in a more diversified morphology of structures such as smectic "batonnets", nematic spindle-like tactoids, and even the possibility for droplet division . Liquid crystals are well-known examples of ordered materials whose nuclei emerge from an isotropic state and have a shape topologically equivalent to a sphere. In the first part of the thesis, we explore experimentally and theoretically the nuclei of columnar lyotropic chromonic liquid crystal coexisting with the isotropic phase that is toroidal in shape. We study the lyotropic chromonic liquid crystal (LCLC) composed by plank-like molecules of disodium chromoglycate (DSCG) with hydrophobic polyaromatic cores and hydrophilic peripheries. The goal is to establish the physical mechanisms in the balance of elasticity and anisotropic surface tension that produce toroidal shapes and establish how these shapes depend on parameters such as molecular concentrations and the presence of a crowding agents. The second part of the thesis will focus on the droplets of chiral and ferroelectric liquid crystal materials.19 0Item Restricted Hydrochemical assessment of an urban groundwater-fed wetland at Sweet Briar Marsh(University of East Anglia, 2024) BinTani, Sharifah Ahmed; Hiscock, Kevinتتعمق هذه الأطروحة بعمق في النظام البيئي المعقد لمستنقع سويت براير، بهدف فهم العوامل العديدة التي تؤثر على جودة المياه. ستكشف الأطروحة عن التفاعلات والتأثيرات المعقدة التي تشكل التوازن الدقيق للمستنقعات من خلال فحص شامل لدرجة الحموضة والأكسجين المذاب والتوصيل ودرجة الحرارة ومستويات المغذيات. يسلط التحقيق الضوء على أن الجريان الزراعي والتوسع الحضري والأنشطة الصناعية تلعب دورًا مهمًا في رفع مستويات النترات والفوسفات، ويرجع ذلك أساسًا إلى الاستخدام المكثف للأسمدة وممارسات إدارة الثروة الحيوانية غير الكافية. تؤدي مستويات المغذيات المرتفعة هذه إلى تلوث المغذيات، مما يزيد من خطر التغذية الزائدة، حيث تحفز المغذيات الزائدة ازدهار الطحالب الضارة وتدهور جودة المياه. تم اقتراح استراتيجيات مختلفة لإدارة المياه لمكافحة هذه التحديات الملحة، بما في ذلك إدارة المغذيات الدقيقة وتدابير مكافحة التلوث. وتؤكد الدراسة على الحاجة الماسة إلى خطط إدارة مصممة خصيصًا والرصد المستمر لحماية الأراضي الرطبة. ويساهم هذا البحث في المعرفة الأوسع بممارسات إدارة الأراضي الرطبة الفعّالة من خلال توفير رؤى متعمقة من الملاحظات الميدانية، مع التأكيد على أهمية مواجهة قضايا جودة المياه المحلية.21 0Item Restricted Quantitation of Taxifolin and its Related Metabolites in Bark Extract by UPLC-MS/MS(University of Edinburgh, 2024) AlIbrahim, Fatimah; Clarke, DavidDrug resistance poses a rising problem for the control of helminth infections in animals, and recently research efforts have highlighted secondary plant metabolites, such as flavonoids, as promising compounds with anti-parasitic activity.1-4 However, accurately quantifying metabolites in complex plant matrices remains challenging. This project addresses this challenge by developing a sensitive analytical method to quantify three flavonoids; taxifolin, quercetin, and luteolin in bark extracts using ultra high-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). The three analytes were separated on a BEH C18 column (2.1mm ×100mm × 1.7µm) using a gradient elution with a mobile phase of water and acetonitrile in 0.1% formic acid. Ion pair monitoring in negative ESI mode using the SRM method was successfully developed for each metabolite. The calibration curve of taxifolin demonstrated excellent linearity over the concentration range of 2-50 µM with a correlation coefficient of 0.99949. Quercetin and luteolin did not demonstrate reliable calibration curves nor were they detected in any bark extracts. Taxifolin was analysed in ten bark samples and four samples were above the level of quantitation. In future work, the quantitation of secondary metabolites in bark samples will be correlated to biological activity to identify possible cost-effective natural anti-parasitic additives for animal feed.13 0Item Restricted Probing Metabolic Pathways using an RccR Based Genetically Encoded Biosensor(Saudi Digital Library, 2023-11-24) Babtain, Ahmad; Dixon, NeilThe study of metabolic pathways is of utmost importance to contemporary biotechnology. However, mapping metabolic pathways is a burdensome process due to the entangled and complex nature of biological systems. Due to the direct involvement of transcription factors in metabolism, biosensors based on them are a powerful tool for researching metabolism. In this study, we used a biosensor vector where the RccR transcription factor regulates the expression of eGFP in response to the metabolite KDPG to investigate the central metabolism of two bacterial species of high relevancy to biotechnology: Pseudomonas Putida and Escherichia Coli, with an experimental focus on the first. Our research demonstrates that acetate, aromatic acids, and fatty acids enter the central metabolism of P. Putida through the TCA cycle. We also show among the aromatic acid, PCA and benzoic acid flux into central metabolism through one metabolic intermediate through a pathway with moderately low metabolic leakage. On E. Coli’s end, we show that acetate and the fatty acid C18:2 enter metabolism through the TCA cycle as well. We also employ bioinformatic databases to show that HexR is closely related to RccR and that the differences between the HexR proteins in P. Putida and E. Coli might show differing interference with RccR’s function. Our results also indicate that P. Putida preferentially consumes glucose, then acetate, and then aromatic acids when presented with mixtures of them. Finally, we saw strong evidence of the presence of a metabolic pathway that leads from acetate into the central metabolism of E. Coli. through acetyl-CoA.24 0Item Restricted Solvation Dynamics of Choline Halide-Based Deep Eutectic Solvents(2023) Alfurayj, Ibrahim Ahmed; Burda, ClemensThe intermittent nature of renewable energy sources requires reliable and cheap long-term energy storage technologies. Redox flow batteries (RFBs) are reliable, scalable, and cost-efficient. Electrolytes are crucial for RFB's performance. Deep eutectic solvents (DESs) are a new class of ionic liquids with relatively cheap and easy synthesis. In addition, their properties are tunable, making DES an excellent candidate for many energy and industry applications. A DES mixture is created by combining hydrogen-bond acceptor (HBA) and donor (HBD) in a specified ratio, producing a mixture with a lower melting point than its constituent components. Varying the type and ratio of HBA results in tunning DES properties. Also, adding co-solvents, such as water, can provide further tunning to DES mixtures. This dissertation aims to study the potential of water addition, HBA choice, and the compositional variation to optimize the solvation dynamics and physicochemical properties of choline halide-based DESs. Besides the most famous Ethaline (choline chloride ChCl): ethylene glycol (EG), 1:2), we reported the first choline fluoride (ChF) and EG-based DES mixture preparation with 1:2 molar ratio. We studied physical properties upon water addition by conductivity, density, viscosity, and ET(30) polarity. NMR, FT-IR, and Raman spectroscopies were used to characterize their structures. Femtosecond transient-absorption spectroscopy (fs-TSA) and NMR-diffusometry were used to study solvation dynamics, providing a powerful tool for studying charge transport properties. Volumetric properties were used to study the effect of water in EthalineF/water and Ethaline/water mixtures. This work also investigated the eutectic enhancement of dynamics and charge transport in Ethaline. We provided excellent tools, such as using B30 as a probe molecule in time-resolved spectroscopy to study solvation dynamics and correlating DES-DES self-interactions to experimental conductivities. Also, proved that water (>1 wt.%) can accelerate charge transport and enhance physical properties. The vibrational spectroscopies indicate that EthalineF has stronger hydrogen bond interactions than Ethaline. In addition, we reported the effect of the solvodynamic radius on the observed lower conductivity in EthalineF compared to Ethaline. Furthermore, based on the NMR diffusion measurements, we assigned the two F-NMR peaks to be EG and choline associated fluorides.17 0Item Restricted Temperature Dependent Partition Coefficients of Cyclohexylamine and Ethanolamine Between Octanol and Water Phases.pdf.pdf(2023-05-13) Alhilal, Ahmed Atiah S; Liu, YongThis study has investigated temperature dependence of octanol/water partition coefficients of cyclohexylamine and ethanolamine in temperature ranges of 5 to 25°C for cyclohexylamine and 17.5 to 25°C for ethanolamine. Experiments are largely based on a method developed by a researcher at the University of South Florida, which can help reduce chemical waste, save effort and time, and generate more reliable results. The study has found that the partition coefficient of cyclohexylamine is higher than that of ethanolamine, consistent with literature results. This also indicates that our approach is probably valid. By investigating correlation between chemical descriptors and partition coefficients of more than 1500 amine chemicals theoretically, we have shown that cyclohexylamine has higher values for descriptors that are positively correlated with logP. In addition, it has been found that temperature influences the partition coefficient of ethanolamine more than that of cyclohexylamine, probably due to smaller molecule size of ethanolamine. The partition coefficient of cyclohexylamine has a seemingly inverse relationship with temperature. On the other hand, temperature dependence of ethanolamine is more complicated. Moreover, we have determined thermodynamics of partition process including enthalpy, entropy, and free energy. Overall, these findings could be used to better assess their potential risks to public health.33 0Item Restricted Per-Halogenated Polycyclic Aromatic Hydrocarbons (PAH)(Saudi Digital Library, 2022-05-23) Abdulghafour, Hadeel; Wilson, David J DPrevious investigations showed that halogen substitutions affect PAH planarity and aromaticity. In this study, a series of 21 linear and non-linear per-halogenated PAHs were considered to explore the minimum energy geometries and their aromaticity. Halogens (Cl, Br, I, and At) change naphthalene from a planar to a propeller- shaped geometry. Per-fluorinated naphthalene remains planar like unsubstituted naphthalene. The larger acene systems with more than two benzene rings have a trend of alternating structures, with the benzene rings being less twisted and halogen atoms alternating in pointing above or below the plane of the benzene rings. Non- linear PAHs structures are twisted, even the fluorinated PAHs. In terms of aromaticity, HOMA and NICS indices were employed to detect π-electron delocalization. Per-halogenation reduces aromaticity significantly, which increases from lighter to heavier halogens. Notably, the distorted structure loses aromaticity. All computed calculations were performed at the B3LYP/def2-SVP level of theory.38 0